TECHNICAL MEMORANDUM

Transcription

1 Califrnia High-Speed Train Prject TECHNICAL MEMORANDUM Gelgic and Seismic Hazard Analysis Guidelines TM Prepared by: Signed dcument n file 11 June 09 Bruce R. Hiltn, PG, CEG, Prgram Engineering Gelgist Checked by: Signed dcument n file 15 June 09 Brian O Neill, PE, GE, Prgram Getechnical Engineer Apprved by: Signed dcument n file 16 June 09 Ken Jng, PE, Engineering Manager Released by: Signed dcument n file 19 June 09 Anthny Daniels, Prgram Directr Revisin Descriptin 0 15 Jun 2009 Initial Release, R0 Prepared by fr the Califrnia High-Speed Rail Authrity

2 This dcument has been prepared by Parsns Brinckerhf fr the Califrnia High-Speed Rail Authrity and fr applicatin t the Califrnia High-Speed Train Prject. Any use f this dcument fr purpses ther than this Prject, r the specific prtin f the Prject stated in the dcument, shall be at the sle risk f the user, and withut liability t PB fr any lsses r injuries arising fr such use. Page 1

3 System Level Technical and Integratin Reviews The purpse f the review is t ensure: - Technical cnsistency and apprpriateness - Check fr integratin issues and cnflicts System level reviews are required fr all technical memranda. Technical Leads fr each subsystem are respnsible fr cmpleting the reviews in a timely manner and identifying apprpriate senir staff t perfrm the review. Exemptin t the System Level Technical and Integratin Review by any Subsystem must be apprved by the Engineering Manager. System Level Technical Reviews by Subsystem: Systems: _Nt Required Print Name: Infrastructure: Signed dcument n file 6/5/2009_ Dnald P. Richards Operatins: _Nt Required Print Name: Maintenance: _Nt Required Print Name: Rlling Stck: _Nt Required Print Name: Page i

4 TABLE OF CONTENTS ABSTRACT INTRODUCTION PURPOSE OF TECHNICAL MEMORANDUM STATEMENT OF TECHNICAL ISSUE GENERAL INFORMATION DEFINITION OF TERMS UNITS DEFINITION OF TECHNICAL TOPIC GENERAL CHSTP DESIGN CONSIDERATIONS CHSTP DESIGN PARAMETERS CODES, REGULATIONS AND APPLICABLE GUIDELINES ASSESSMENT AND ANALYSIS SUMMARY AND RECOMMENDATIONS SOURCE INFORMATION AND REFERENCES DESIGN MANUAL CRITERIA GEOLOGIC AND SEISMIC HAZARD IDENTIFICATION AND EVALUATION GROUND RUPTURE LIQUEFACTION AND OTHER SEISMICALLY-INDUCED GROUND DEFORMATION TSUNAMI AND SEICHE LANDSLIDE AND SLOPE STABILITY KARST TERRAIN AND ABANDONED MINES VOLCANIC HAZARDS SOIL AND ROCK EROSION LAND SUBSIDENCE COLLAPSIBLE SOIL EXPANSIVE SOILS HAZARDOUS MINERALS FLOOD HAZARD AND DAM INUNDATION GEOLOGIC AND SEISMIC HAZARDS GIS DATABASE GEOLOGIC AND SEISMIC HAZARD EVALUATION REPORTS Page ii

5 ABSTRACT This Technical Memrandum prvides guidance fr gelgic and seismic hazards evaluatins based primarily n existing guidance dcuments and data n gelgic and seismic hazards, and supplements these guidelines with additinal clarificatin and scpe where applicable. These guidelines are generally cnsistent with ther key guidance dcuments prepared primarily by the Califrnia Bard f Gelgists and Gephysicists and Department f Transprtatin. Based n these dcuments, gelgic hazards and hazardus minerals addressed herein include: Grund rupture alng active faults Liquefactin and ther seismically-induced grund defrmatin Tsunami and seiche Static and seismically triggered landslides and slpe stability Karst terrain and abandned mines Vlcanic hazards Ersin r scur Land subsidence Cllapsible sils Expansive sils Flding and dam inundatin Hazardus minerals This technical memrandum has been prepared t highlight available data develped during the Prgrammatic EIR/S and prvide guidance n methds fr identifying and evaluating the gelgic and seismic hazards fr preliminary engineering. Slpe stability and seismic grund mtin hazards are addressed separately in TM Getechnical Investigatins Guidelines and TM Interim Grund Mtin Analysis Technical Memranda. Page 1

6 6.0 DESIGN MANUAL CRITERIA 6.1 GEOLOGIC AND SEISMIC HAZARD IDENTIFICATION AND EVALUATION Preliminary qualitative evaluatin f gelgic and seismic hazards shall be perfrmed in advance f getechnical and seismic hazard analyses. This will enable Designers t develp investigatin and analysis prgrams based n an understanding f any gelgic r seismic hazards identified t have a ptential impact t the elements f the CHSTP. Gelgic and seismic evaluatins f ptential hazards shall be perfrmed under the direct supervisin f a prfessinal gelgist r engineering gelgist. The Gelgist shall wrk in clse cmmunicatin with the prject Designer and Getechnical Engineer t cnsider the hazard implicatins t the elements f the design, cnstructin, and/r peratin. Gelgic and seismic hazard evaluatins shall generally address the fllwing cnditins: Gelgic setting Physigraphy and tpgraphy Surface and grundwater cnditins Surface sil and rck cnditins Presence and influence f gelgic hazards Cnceptual avidance r mitigatin alternatives Recmmendatins fr future investigatins if necessary Discrepancies, if any, between the CHSTP fault database and the results f segment specific evaluatins shall be presented in the gelgic and seismic hazard reprts. Where applicable, risk-based r risk-infrmed methds are recmmended fr hazard analysis. The quantitative analysis and mitigatin design f hazards such as liquefactin r slpe stability are addressed separately. Althugh seismic surce characterizatin is discussed in this dcument, develpment f quantitative grund mtin hazard values fr input t seismic design parameters fr the CHSTP will be prvided separately in the TM Grund Mtin Analysis Guidelines. N attempt is made t duplicate the guidelines. Because f the clse relatinship between these quantitative analyses and gelgic and seismic hazard evaluatins, it is critical that the Gelgists respnsible fr the gelgic and seismic hazard evaluatins be included in any decisins and subsequent evaluatins that rely upn this data. This includes review f key dcuments and findings related t hw these hazards are treated in the design f the system elements. The gelgic and seismic hazard evaluatins shall be perfrmed under the supervisin f a Califrnia licensed Prfessinal Gelgist r Certified Engineering Gelgist. The prject Gelgist shall be invlved with subsequent evaluatins and site investigatins. In additin, each gelgic and seismic hazard evaluatin shall, at a minimum, include a site visit and preliminary field mapping as apprpriate and where ever practical. The fllwing subsectins prvide specific guidance and reference the relevant guidance dcuments frm which the specific guidance was develped. The guidance discussed in the fllwing subsectins is preferential t Caltrans guidance where apprpriate Grund Rupture Fur steps are recmmended fr fault and grund rupture evaluatins. These steps are literature review, recnnaissance, pale-seismic trenching, and mitigatin design, as needed. Fr the high-speed train prject, rupture f the grund surface shall be addressed at any lcatin where a mapped r therwise suspected Hlcene fault (i.e. mst recent mvement within the past 11,000 years) cnsistent with current Califrnia regulatins cntained in Nte 49 (CGS, 1996), SP 42 (CGS, 2007), and Nte 48 (CGS, 2007). These faults are hereafter referred t as active faults. These guidelines prvide minimum standards fr evaluatins f faults. Page 10

7 Cmpilatin and Review f Available Data Grund rupture evaluatins shall cmmence with review f the Gelgic and Seismic Hazards GIS Database that was cmpiled fr this prject. This database is in GIS frmat and will be made available cncurrent with the issuance f this dcument. The database includes a Quaternary fault database, which was prepared by appending the Califrnia Quaternary fault database Bryant (2005) with fault data frm the USGS Natinal Fault Database. A secnd fault database was btained fr pre-quaternary structures (CGS, 2000) and includes faults and fld gelgic structures. Histric earthquakes are cntained in the ANSS (2008) database. All three databases are available in GIS frmat. The attributes cntained in the appended fault database include the fault name, displacement behavir, length, reference number (relative t CGS and USGS external databases), age f faulting, length f mst recent rupture segments, slip rate, and dip directin. The attributes cntained in the appended ANSS earthquake database include date (year, mnth, day, hur, secnd), lcatin (latitude/lngitude), and magnitude. Althugh these databases are cmprehensive, lcal faults r splays, and unrecrded earthquake data may be missing. As such, research alng specific alignments shall include review f lcal gelgic maps and reprts, including review f CGS Fault Evaluatin reprts (FER) where available. These databases shall be reviewed as a screening evaluatin t identify all pssible active faults within ne mile f any design element f the CHSTP. The ANSS database has been included t identify ptential seismic alignments where unmapped r therwise unknwn faults may exist in prximity t the CHSTP elements. A pre-quaternary fault database is included t allw identificatin f pre-quaternary faults that may have Quaternary activity elsewhere alng a tectnically related structure. Cllectively, these lcatins shall be identified and digitized at a Prgram Level and disbursed t Designer fr their further evaluatin based n lcal and mre cmprehensive evaluatin. It is prvided t the Designer fr initial identificatin and evaluatin f seismic surces fr develpment f the seismic surce mdel (earthquake magnitude frm surce and distance t CHSTP system element(s) fr input int develping the grund mtin mdel and hazard curves fr input t Prject specific seismic design criteria Gelgic Recnnaissance At lcatins where active faulting is suspected t be cincident with r within the area f CHSTP peratins and facilities, a gelgic recnnaissance will be needed t grund-truth mapped fault traces. This recnnaissance shall begin with review f available aerial phtgraphs, LiDAR data, satellite imagery, and tpgraphic infrmatin. The lcatins shall then be reviewed in the field t assess the presence f gemrphic features assciated with faulting such as escarpments, pressure ridges, sag pnds, seeps/springs, vegetatin cntrasts, r deflected drainages. All such features shall be dcumented n a gelgic field map. If sufficient field data is available t dcument that the fault r fault zne is utside f the area f high-speed train peratins, n further fault evaluatin is required. Otherwise, a site specific investigatin pssibly including pale-seismic trenching will be necessary Pale-Seismic Trenching If existing pale-seismic trenching data is available, it may be reviewed and used as a basis fr lcating the fault and prviding its rupture characteristics t the design team; hwever, if either a knwn active fault r suspected active fault is lcated near t r at the lcatin f a CHSTP facility, explratry trenching acrss the fault may be necessary t assess its rupture characteristics fr input t design. The bjective f pale-seismic trenching is t prvide the Designer with fault lcatin and rupture characteristics that may influence the design elements. In general, these characteristics may include but are nt limited t lcatin f strands with Quaternary activity, secndary znes f displacement, displacement sense f mvement, displacement per event, and displacement rientatin(s). This evaluatin shall als address the degree f certainty f infrmatin as a basis fr determining the extent f mvement and lcatins affected. Page 11

8 Grund Rupture Mitigatin Design The high-speed train alignment and prject facilities shall avid all active faults t the extent pssible. If these faults cannt be avided, t the extent pssible, the CHSTP system cmpnents at that lcatin shall be designed t accmmdate ptential rupture including bth primary and secndary rupture znes. In rder t meet the CHSTP perfrmance criteria, grund rupture will need t be mitigated t meet the Safety Perfrmance Level (SPL) and Operability Perfrmance Level (OPL) criteria. Fr the SPL, the system shall be designed t accmmdate fault rupture and sustain limited structural damage such that the structure can quickly be repaired and the train peratins can resume within a specified time frame. Fr the OPL, system elements critical t peratin f the train will need t be designed s that structural damage frm an earthquake where surface fault rupture ccurs is minimal and trains can perate safely, at the maximum perating speed. These tw perfrmance levels are defined as the Design Basis Earthquake (DBE) and the Lwer-level Design Basis Earthquake (LDBE), respectively fr grund rupture. This nmenclature is adpted frm the seismic design criteria in rder t prvide cnsistency between the design fr earthquake and fault rupture cnditins. Buildings Statins and Strage/Maintenance Facilities) At a minimum, terminal and intermediate statins and ther buildings key t peratin f the highspeed train shall avid active fault znes. Therefre, fr surface fault displacement neither the SPL nr OPL criteria need t be achieved under these circumstances. If faults have been identified at the planned lcatins f statins and key peratinal buildings but whse mst recent faulting is unknwn, the fault shall be evaluated. If cnfirmed that the last mvement was pre-hlcene mitigatin wuld nt necessarily be required. At-Grade Track Sectins In general terms, the DBE cnditin can be mitigated using early warning and shutdwn telemetry systems t achieve the SPL criteria. Ballast and track shall be designed t accmmdate fault rupture that with allw restratin f peratin within a reasnable time frame (t be defined by Prject team). The LDBE can als be mitigated by design f ballast and track sectin t accmmdate LDBE displacement. This may require alignment f track perpendicular t the fault alignment t reduce the zne f influence. Where high slip rate faults are crssed (i.e., large displacements), the rail may need t be designed s that it can readily tlerate such grund displacements r the ptential range f grund displacements shall be treated prbabilistically (see discussin under Mitigatin f Fault Rupture ). Tunnels The Basis f Design reprt has identified that it is desirable fr the hrizntal and vertical alignment t crss majr fault znes at-grade withut structures at active fault crssings where mitigating designs can be mre cst-effectively emplyed. Faults shall be crssed perpendicular t reduce the extent f damage. Expert seismlgists, tunnel Designers and cntractrs cncluded that majr fault crssings wuld require fault chambers that are extremely cstly. Hwever, fr lw slip rate faults and smaller displacements, nrmal tunnel design standards may accmmdate limited fault displacement (maximum displacement t be determined by Designers). The Designer shall identify the presence f any majr faults irrespective f age f mvement in that these znes will need t be evaluated frm a seepage and bring cnditin standpint. Structures Aerial and Bridge Segments Structures carrying high-speed trains shall avid paralleling r crssing active fault lcatins. Where nt avidable, structures will need t be designed t accmmdate the DBE fault displacement in a manner that allws restratin f peratin in a reasnable perid f time meeting the SPL perfrmance criteria. The LDBE fault rupture will als need t be cnsidered in the design f structures s that structural damage will be minimal r nn-existent and trains can cntinue perating safely at the maximum perating speed. Page 12

9 Mitigatin f Fault Rupture Where grund rupture alng active faults immediately adjacent t r crssing high-speed train system elements cannt be accmmdated thrugh design measures, fault displacement will need t be characterized prbabilistically. The fllwing displacement characteristics shall be addressed: Sense r directin f mvement Orientatin f displacement Magnitude f displacement Displacement histry Rupture length and depth These analytical results will be needed t supprt Prbabilistic Fault Displacement Hazard Analysis (PFDHA) methd t address the SPL (DBE) and OBL (LDBE) prbability scenaris within the design life f the high-speed train structures. The PFDHA shall be perfrmed in general accrdance with methds described by Yungs et al (2003) and Cppersmith and Yungs (1992). The displacement apprach methd described in Yungs et al (2003) is the preferred apprach. Secndary rupture shall be estimated using direct bservatin methds (i.e. pale-seismic trenching) r prbabilistic methds prvided by Bray (2005) Other Uses f the Grund Rupture Hazard Analyses Data The infrmatin cmpiled in the preliminary fault hazard studies and the analyses perfrmed frm this hazard assessment will be used as input t the develpment f seismic surce characterizatin mdel(s) fr the quantificatin f vibratry grund mtin hazards. The parameters frm the fault hazard studies prvide key input t the develpment f the seismic surce characterizatin mdel(s) and calculatin f earthquake magnitudes frm thse seismic surces mst significant t the CHSTP system. The guidance fr the seismic surce characterizatin (SSC), grund mtin characterizatin, and prbabilistic seismic hazard analysis will be prvided in the TM Grund Mtin Analysis Guidelines Liquefactin and Other Seismically-Induced Grund Defrmatin Liquefactin guidelines prvided in SP 117 (CGS, 2008) are applicable fr identifying liquefactin and ther seismically-induced grund defrmatin fr prject design. Guidance fr apprpriate grund mtin parameters t utilize in liquefactin analyses is prvided in the TM Grund Mtin Analysis Technical Memrandum. Quantitative liquefactin analysis methds are described in the Getechnical Investigatin and Getechnical Analysis Guidelines Technical Memrandums. Fr purpses f the Gelgic and Seismic Hazards Evaluatins, ptentially liquefiable sites shall be identified using the screening prcedures described in SP 117 (CGS, 2008) and als as clarified in Suthern Califrnia Earthquake Center (SCEC) (1999), Recmmended Prcedures fr Implementatin f SP117 Guidelines fr Analyzing and Mitigating Liquefactin Hazard in Califrnia. These tw guidelines generally require a cnservative assessment f prtins f the CHSTP that cincide with areas f present and/r future ptential grundwater within 50 feet f the grund surface and the presence f Hlcene depsits. Since the majrity f the CHSTP ftprint exists within areas f relatively high grund mtins, all areas that meet this grundwater and surface earth material criteria shall be identified as ptentially liquefiable requiring further investigatin and analysis. Guidelines fr evaluatin f lateral spreading shall als fllw thse available in SP 117 (CGS, 2008). Distances t pen channels and ther free faces shall be measured alng with embankment slpe heights and ratis and included in gelgic and seismic hazard assessment reprts fr use in cnjunctin with liquefactin analyses. The ptential fr ther types f seismically-induced grund defrmatin, such as differential cmpactin and seismic settlement, shall als be evaluated. Areas underlain by dry, uncnslidated sediments may be prne t this type f defrmatin and shall be nted in the gelgic and seismic hazard reprt. Page 13

10 6.1.3 Tsunami and Seiche Tsunami and seiche evaluatin guidelines are nt generally available. Ptential fr tsunami ccurrences alng the Califrnia castline is available frm the CGS, the USC Tsunami Research Center, and USGS. It shall be reviewed in cnjunctin with the prject ftprint t identify lcatins where ptential tsunami inundatin may influence peratin. Similar mapping is nt available fr seiche. Therefre, it will be necessary fr the gelgic and seismic evaluatin t identify any lcatins where large bdies f water exist r are planned upstream f the CHSTP and its cmpnents. The ptential fr seiche shall be discussed relative t surce (landslide, fault displacement, etc.) available freebard and general drainage cnditins between the water bdy and high-speed train facilities Landslide and Slpe Stability The ptential fr reactivatin f existing landslides and ptentially unstable slpes shall be identified and evaluated in the gelgic and seismic hazards evaluatin. This evaluatin shall cnsider static (i.e. nn-seismic) as well as seismically induced slpe failure ptential. Existing landslide databases are presently being catalgued by the CGS and thers, but are nt yet available fr cverage f the entire prject. Guidance dcuments that prvide evaluatin guidelines fr landslides and ptentially unstable slpes and are applicable t the CHSTP include thse frm CGS, Caltrans, BGG, and SCEC. The mst applicable f these guidance dcuments is the Recmmended Prcedures fr Implementatin f CGS Special Publicatin 117 Guidelines fr Analysis and Mitigatin f Landslides in Califrnia (SCEC, 2002). The evaluatins shall fcus n thse prtins f the alignment that cincide with mderately steep r steeper tpgraphy. If ptential instability exists and warrants further quantitative analysis and/r mitigatin design, the Gelgist shall wrk clsely with the prject Getechnical Engineer and the guidelines fr Getechnical Investigatins and Getechnical Analyses shall be fllwed. Bth the supervising Gelgist and Getechnical Engineer shall be experienced in landslide recgnitin, investigatin, and mitigatin. The evaluatin f landslides and unstable slpes requires fur fundamental steps: Backgrund research Field mapping and investigatins Data evaluatin Presentatin f findings Backgrund research entails the use f existing dcumentatin f mapped r therwise recgnized landslides. These data are available frm the CGS, Caltrans, and generally cnsist f maps and databases (i.e. GIS) catalguing knwn landslide lcatins. CGS maps shwing landslides are available at the tw-degree sheet detail (1:250,000) and are lcally available at mre detailed scale. In sme instances, cities and cunties have inventried landslides and shall als be cnsulted. Backgrund research als includes the evaluatin f aerial phtgraphs, LiDAR and ther remte imagery and interpretatin f tpgraphic maps fr evidence f landslide-related gemrphic features. Field mapping is typically perfrmed in advance f and independent t field investigatins. Where backgrund research identifies knwn r suspected landslide features, field mapping is required t cnfirm the presence and apprximate limits f landslides. Phtgraphs and ntes are needed t dcument the presence r absence f landslide features bserved during field mapping. Investigatin f landslides will be needed where backgrund research and mapping suggest the presence f a landslide within the area f influence f the CHSTP design. This determinatin will need t be made by the Designer subsequent t any attempt t avid the landslide hazard. The many investigatin methds are clearly defined in Landslide Investigatin and Mitigatin Special Reprt 247 (TRB, 1996). Additinal regulatins and guidance may be available at a city r cunty level and shall be adhered t where available. Data evaluatin generally cnsists f interpretatin f the landslide gemetry and failure mechanism(s) including surface drainage cnditins and subsurface grundwater cnditins. Page 14

11 This evaluatin shall include develpment f maps and crss sectins prviding threedimensinal interpretatin f the landslide limits and cnditins. In additin t existing landslide and their ptential fr reactivatin, unstable frmatins and steep terrain shall be evaluated t assess areas f ptential instability. This evaluatin shall nt be limited t natural slpes adjacent t the alignments and r supprting facilities and statins but shall als address the ptential adverse influence f cnstructin activities such as excavatins. Reprts addressing the evaluatin f landslide shall effectively dcument the methds, findings, and interpretatin f landslide gemetry, failure mechanism(s), and prvide general cnclusins addressing the relative likelihd f reactivatin Karst Terrain and Abandned Mines Sink hles can ccur as a result f a number f types f near surface vids including mine wrkings and karst tpgraphy. Karst tpgraphy ccurs when slutin cavities develp in rck having a high slubility such as limestne, dlmite, r halite rich rck. Earth materials suspected t be susceptible t develpment f karst features shall be evaluated based n available gelgic maps. Mine wrkings are generally shwn n USGS tpgraphic quadrangles and have been digitized by the USGS n the MRDS (Mineral Resurces Database System) fr the 11 western U.S. states including Califrnia (USGS, 2002). While this database des nt address the ptential fr surface defrmatin r cllapse f mine wrkings, it des prvide a cmprehensive listing in GIS frmat f all knwn and dcumented mine facilities. Guidance prvided fr karst terrain and abandned mines evaluatin is based n CGS Nte 48 (2007). If an area f knwn r suspected karst terrain r mine wrkings is suspected, it shall be further reviewed based n available literature and maps and field recnnaissance. If present, the cnditins shall be identified by maps and crss sectins and cmmunicated t the Designer. If the feature(s) cannt be avided, detailed investigatin and getechnical analysis f the subsurface vids and verlying sil and/r rck will be required. This analysis shall address the ability f the verlying rf sil and/r rck t bridge ver the feature given the design lad cnditins. These analyses wuld als be needed when designing pssible mitigatins t prtect the cnstructin and peratin f the high-speed train frm the cllapse f subsurface vids Vlcanic Hazards Fr purpses f the CHSTP, there are several Califrnia vlcanic hazard znes (USGS, 1998) including the Cascade, Lassen Peak, Clear Lake, Lng Valley-Mammth, Amby Crater, and the Saltn Buttes. These vlcanic centers appear t be sufficiently remved frm the CHSTP ftprint and likely d nt pse a hazard t the HST system: hwever, this shall be cnfirmed in subsequent evaluatins. Guidelines fr the evaluatin f vlcanic hazards in Califrnia are nt well defined. CGS (2001) Nte 52 indicates that evaluatin f vlcanic hazards shall include an evaluatin f the ptential fr lava flw, ash fall, and vlcanic eruptin. CGS (2007) Nte 48 Checklist fr the Review f Engineering Gelgy and Seismlgy Reprts fr Califrnia Public Schls, Hspitals, and Essential Services Buildings prvides a brief explanatin f evaluatin guidelines and expectatins. This guidance emphasizes the use f existing literature and maps identifying the lcatin f knwn r ptential vlcanic hazards. Since the high-speed train alignment is nt in clse prximity f knwn active vlcanic centers, the nly ptential vlcanic hazard t cnsider is that f ash fall. This ptential hazard shall be addressed by determining the expected accumulatin f ash at the nearest HST facility based n existing infrmatin, analg studies f field bservatins. If there is a ptential fr accumulatin f ash then that shall be reprted in the technical dcumentatin Sil and Rck Ersin Ersin f sil and/r rck due t runff, stream flw, wave actin, r severe wind culd remve sil and rck supprt fr infrastructure cmpnents and have adverse affects n the CHSTP. This includes ptential cases where the alignment may parallel a water curse, and high water culd erde the side embankment f the riverbed threatening r undermining the trackbed by sustained r cumulative ersin. Because this cnditin requires an understanding f bth the sil and rck cnditins as well as the runff and drainage cnditins, it will be imperative that this evaluatin is perfrmed with a hydrlgist and the Designer. The evaluatin f erdible sil Page 15

12 and rck shall be initiated by defining lcatins where drainage remains uncntrlled cincident with expsed sil r rck such as natural drainages, bridges, and castal lcatins adjacent t prject facilities. Scur analysis is nt cnsidered in this technical memrandum and will be assessed independently. The preliminary ersin/scur evaluatin shall prvide an initial evaluatin f sil and rck cnditins where flw/wave actin is anticipated and shall qualitatively address the sil r rck parameters prvided by Annandale (1995) as a screening prcess. If qualitative evaluatin suggests ersin/scur is highly unlikely given cnservative assumptins, n further actin will be required. If the ptential cannt be ruled ut, subsequent ersin/scur analyses is required t quantify the ptential and, if needed, the design f armament systems Land Subsidence Land subsidence is unique frm ther ptential gelgic hazards in that it is a lng term cnditin that is nt likely mitigated at a prject level. Subsidence in Califrnia has been induced by withdrawal f petrleum and gas r grundwater and in sme instances cmpactin f rganic rich sediments that have decayed with time, such as in the Delta regin. Althugh the majrity f subsidence has ceased r decelerated significantly, sme subsidence cntinues in the Central Valley and Delta regins. This may be f cnsequence since such subsidence wuld have lng term influence n the surface elevatin f track and supprting facilities and therefre shall be further evaluated n a lcal basis. The evaluatin shall begin with a review f recrds dcumenting grund surface subsidence and shall generally fcus n thse areas f histric subsidence as shwn n maps prvided by Ireland (1966). Regulatry guidance fr the evaluatin f subsidence is nt available. CGS Nte 48 (2007) prvides a cursry discussin f evaluatin methds. In mst instances, subsidence has nt histrically ccurred r has strng dcumentatin fr cessatin in recent histry and a strng case can be made fr the absence f subsidence during the prject life expectancy. Lcatins where future subsidence cannt be ruled ut shall be carefully evaluated with available gedetic infrmatin and an estimate f future subsidence ptential and rate shall be assessed fr the affected CHSTP element s tlerance t this settlement Cllapsible Sil Cllapsible sils are thse sils that tend t underg rapid cnslidatin when wetted (i.e. hydrcnslidatin). A number f publicatins and maps identify areas where these sils are mst likely t ccur. Cllapsible sils are generally lcated in arid climate areas where sils have nt experienced high misture cntents and debris flw depsits where sils were depsited rapidly. Based n a review f publicatins, the ptential ccurrence shall be evaluated frm a gelgic perspective and identified fr further investigatin and analysis by the Getechnical Engineer Expansive Sils Expansive sils will be evaluated during getechnical investigatins as defined in the Getechnical Investigatin Guidelines. Expansive sils are knwn t cincide with high plasticity and fine grained clays typical t delta, lacustrine, and marine depsits that shall be qualitatively identified by the gelgic and seismic hazards evaluatin. Lcatins where these types f depsits may ccur shall be identified in the gelgic and seismic hazards evaluatin reprt and cmmunicated t the prject Getechnical Engineer Hazardus Minerals Hazardus minerals evaluatins shall cnsider the ptential ccurrence f naturally ccurring asbests (NOA), mercury, r radn. NOA tends t ccur in mafic r ultramafic rck r sediments derived frm ultramafic rck. The CGS (2008) website prvides currently available maps depicting the extent f NOA where it is mst likely t ccur. Evaluatins shall be perfrmed in accrdance with CGS (2002) Special Publicatin 124 fr gelgic evaluatins f NOA. Threshld values and mitigatin requirements are prvided by the Califrnia Air Resurces Bard (CARB) fr quarrying, earthwrk, and surface mining peratins in the Asbests Airbrne Txic Cntrl Measure (ATCM, 2004). Natural surces f mercury include vlcanes, ht springs, and natural mercury depsits. Surces related t human activities include cal cmbustin, waste incineratin, certain industrial activities and sme mining activities. Guidance fr mercury evaluatin is prvided by CGS (2008) Page 16

13 and threshld values and mitigatin is prvided by the USGS in the reprt, Mercury in the Envirnment (USGS, 2000). Radn gas is a naturally-ccurring, radiactive gas that is invisible and drless. It frms frm the radiactive decay f small amunts f uranium and thrium naturally present in rcks and sils. Radn gas may be harmful if cncentrated in enclsed spaces where ambient cnditins are nt available t disperse the gas. Radn is mst cmmnly assciated with plutnic rcks and shale. Infrmatin addressing the lcatins where radn is mst likely t ccur is prvided by the CGS (2008) and further regulatry infrmatin is prvided in Gelgic Cntrls n the Distributin f Radn in Califrnia (Califrnia Department f Health Services, 2003) Fld Hazard and Dam Inundatin Areas f ptential fld hazard have been mapped by FEMA (2008) Fld Insurance Rate Maps (FIRM) and shall be reviewed and summarized in the gelgic and seismic evaluatin reprt. These lcatins shall be cmmunicated t the prject hydrlgist fr further quantitative evaluatin, as needed. FIRM maps are available at the FEMA Map Service Center n the internet at Dam inundatin maps are available frm varius surces and can be btained fr mst areas. Such maps are cmmnly available in city and cunty general plans as part f their safety elements. Areas f ptential dam inundatin hazard shall be reviewed and summarized in the gelgic and seismic evaluatin reprt. 6.2 GEOLOGIC AND SEISMIC HAZARDS GIS DATABASE The gelgic and seismic hazards addressed herein will be accmpanied by a Gespatial Database that prvides unifrm, prject-wide data intended fr use by Designers in cnjunctin with this Technical Memrandum. In general, this GIS Database includes: Active Fault and Related Surce Characteristics Pre-Hlcene, Inactive Faults Lcatins Statewide Landslides Gelgic and Sil Units Statewide Grundwater Depths Ptential Tsunami Lcatins Sil Prfile Types Vlcanic Hazards Hazardus Minerals (e.g. Naturally Occurring Asbests) These data are cntained within the Gelgic and Seismic Hazards GIS Database,lcated n the PrjectSlve website: GEOLOGIC AND SEISMIC HAZARD EVALUATION REPORTS Gelgic and seismic hazard reprts shall be prepared t summarize data, methdlgies, analysis, and cnclusins. Gelgic and seismic hazard evaluatin reprts shall be prepared in advance f ther getechnical reprts in rder t prvide a gelgic framewrk fr future getechnical studies. Reprts shall be prepared in a manner cnsistent with CGS Nte 52 (2001); BGG (1998); AEG (1993) guidance fr preparatin f gelgic, engineering gelgic, and gephysical reprts; and in general accrdance with Chapter 7 f Standard Envirnmental Reference (SER) addressing tpgraphy, gelgy, seismic, and sils studies (Caltrans, 2007). In accrdance with these guidance dcuments, all gelgic and seismic hazard evaluatin reprts shall be prepared under the direct supervisin and bearing the signature and stamp, f a Califrnia licensed Prfessinal Gelgist (PG) r Certified Engineering Gelgist (CEG). Gelgic and seismic hazard evaluatin reprts shall be reviewed by similarly qualified gelgists and engineering gelgists based n the abve-referenced guidance dcuments and CGS (1986) Nte 41 Guidelines fr Reviewing Gelgic Reprts. Because the hazard reprts will be relied upn by Getechnical Engineers, they shall als be reviewed by the prject Getechnical Engineer. Page 17

14 Fr cnsistency with the grund mtin analyses, the results f gelgic and seismic hazard evaluatins shall be prvided t the Getechnical Engineer and seismic design engineer fr their evaluatin at a quantitative level as input t the getechnical investigatin and analysis prgresses. In additin, the preparatin f getechnical reprts shall utilize the infrmatin cntained in these gelgic and seismic hazard evaluatins frm a qualitative standpint and shall address hw the gelgic and seismic hazards have been bth quantified and determined t be incnsequential t the high-speed train perfrmance, r the methd f in-situ and/r prject mitigatins emplyed. The Getechnical Engineer will evaluate each f the identified gelgic r seismic hazards t determine whether they are within the tlerance f the CHSTP elements. If these hazards are fund t exceed prject tlerances, subsequent and mre detailed analysis is warranted and shall be perfrmed by the respnsible Gelgist and prject Getechnical Engineer. This will ensure that getechnical investigatins and analyses perfrmed under separate guidance are cnsistent with characterized gelgic cnditins and hazards. The results f each Gelgic and Seismic Hazard Evaluatin shall be summarized in a Gelgic and Seismic Hazard Evaluatin Reprt. Fllwing is a general reprt frmat that can be used fr reprt preparatin: An intrductin, including the scpe f wrk, prject descriptin, site descriptin, and summary f previus investigatins (if any); A summary f the reginal and lcal gelgic and seismic cnditins, prviding descriptins f lcal gelgic units, gelgic structure, faulting, histrical seismicity, landslides, and grundwater cnditins; A summary f gelgic and seismic hazards that have the ptential t adversely impact the prject; Cnclusins regarding the impact f identified hazards and ptential mitigatin measures; Recmmendatins fr future studies, and A list f references. In additin, each reprt shall include a site lcatin map, reginal and lcal gelgic maps, gelgic crss-sectin(s), and ther maps and figures where deemed apprpriate. Faults depicted n the gelgic maps shall cincide with thse frm the CHSTP database. Discrepancies between the CHSTP database and the results f the study shall be presented in the hazard evaluatin reprt. Page 18